Women grow beard because of too much male hormone, often caused by polycystic ovarian syndrome or by the loss of estrogens after menopause, which accelerates hair growth. This especially popular among Asian women.
Its hereditary. Thin hair is called vellus and during puberty some hairs (in certain areas become thick and coarse-pubic area, arm pits, etc) become terminal hairs. but unfortunately some womens facial hair doesnt stay vellus it becomes terminal hair also. due to too much male hormones.